Weak electric fields may disrupt cell membranes

STANFORD -- Stanford University chemists have demonstrated that external
electric fields can have a disruptive effect on a simple model of a
biological membrane.

Writing in the Feb. 4 issue of the journal Science, chemistry Professor
Harden M. McConnell and postdoctoral fellows Ka Yee C. Lee and Jurgen F.
Klinger report that weak but non-uniform electric fields can cause
significant disruptions in such a membrane under conditions that may be
present in living cells.

"This does not prove that external electric fields have a deleterious
effect on cell membranes, but it suggests that they might have such effects,"
says McConnell.

There is considerable interest in determining how electromagnetic fields
affect living cells. Population studies have shown statistical links between
some types of cancer and the very weak electrical fields to which people are
commonly exposed from sources such as household appliances and power lines.
But, recognizing the limitations of such statistical associations, the
scientific community has demanded that a mechanism by which weak electric or
magnetic fields can cause harm be established before accepting such links as
real.

One proposed mechanism for such effects is that electric fields might
affect cell membranes in ways that could trigger cells to function
inappropriately.

An example of inappropriate triggering caused by a different type of
stimulus is asbestosis: Immune system killer cells react to asbestos fibers
as if they are invading bacteria and produce toxins that have no effect on
the fibers but cause this serious lung disease by killing the cells in the
fibers' vicinity.

To test whether electric fields have the power to disrupt membranes,
McConnell and his colleagues devised a conceptually simple experiment. In a
small covered dish with a glass pipette mounted vertically at its center,
they created a Langmuir film, a simple membrane made of lipid molecules
floating on a water surface. (Langmuir films have been used for many years to
study membrane properties.)

By running a wire through the vertical tube and connecting it to a power
source, the researchers were able to expose the membrane to an electric field
that varied with distance from the wire.

Next, the scientists varied the pressure in the dish. Changing the
pressure caused an important factor called the critical temperature to change
as well. The critical temperature is the temperature at which the membrane
undergoes a process called phase separation. In essence, the membrane breaks
down into its constituent ingredients, much as salad dressing separates into
oil and vinegar.

Finally, they used a technique called fluorescent microscopy to monitor
the condition of the membrane.

"Basically, our experiment shows that as the critical temperature
approaches the ambient temperature, the weaker the electric field required to
disrupt it," McConnell says.

That is significant because previous experiments suggest that cell
membranes adjust their chemical make-up so that they remain very close to the
critical temperature, the scientist reports. This gives the membranes the
plasticity they need to hold in place the array of proteins that are attached
to them.

As a consequence, even weak electrical fields have the capacity to cause
large changes in the lipid organization of membranes. If the fields can
disrupt the lipids, then they also should be able to disrupt the protein
receptors on the membrane surface and so trigger an inappropriate cellular
response, the scientist argues.

McConnell and his colleagues are following up on this study with
additional research to look at the effects that electromagnetic fields
produced by alternating currents have on living cell membranes.

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